On some versions of Linux, include KDE Neon and Manjaro XFCE, the Snapcraft package complains with an error:
Mailspring could not store you password securely. Make sure you have
libsecretinstalled and a keyring is present. For more information, visit http://support.getmailspring,com/hc/en-us/articles/115001875571
Snapcraft packages need to be self-contained. While it is often possible to manually install
gnome-keyring, there has to be a way to take care of this internally in the Snapcraft package.
P.S. A Flatpak package may possible also mitigate this scenario. Flatpak Distribution on Linux